Grinding and mixing apparatus and method



April 12, 1938. A. D. KIRKLAND GRINDING AND MIXING APPARATUS AND METHOD Filed Dec. 18, 1931 4 Sheets-Sheet l 6 W x 2 rd M 3 5 Z 1 u ,9 9 4. k. 7 E P n 9 j 1 J 2 2n n a 2 H 4 2 1 2 6 72 INVENTOR ARQZHIBALD D. KIRKLAND ATTORNEY 4 Sheets-Sheet 2 April 12, 1938. A. D. KIRKLAND GRINDING AND MIXING APPARATUS AND METHOD Filed Dec. 18, 1931 D. KIRKLAND INVENTOR ARCHIBALD ATTORNEY April 12, 1938. A. D. KIRKLAND GRINDING AND MIXING APPARATUS A ND METHOD 4 Sheets-Sheet? Filed Dec. 18, 1931 INVENTOR ARCHIBALD 0. KIRKLAND ATTORNEY April 12, 1938. A. D. KIRKLAND v GRINDING AND MIXING APPARATUS AND METHOD Filed Dc. 18, 1931 4'Sheets-Sheet 4 fie ATTORNEY the final product, and delivering homogeneous state,

takes place and a Patented Apr. i2, 138 I ENG AND MIXING APARATUS METHOD Archibald ID. Kirkland,

to .iabez Burns & Sons,

New York, N. Y., assignor Inc., New York, N. Y,

ill Glaims.

This invention relates to apparatus for grinding and mixing dry materials such as coiiee and chaff and has for its object to produce a homogeneous, non-stratifying mixture derived from various sized particles of material ranging all the way from dust to large flakes and granules.

Another object of the invention is to provide a simple, compact device for thoroughly mixing .dry comminuted .materials without tossing or aeration and for extruding the mixed materials under controlled conditions to prevent subsequent separation oi the light and heavy particles.

Another object of the invention is to provide a combined grinding and mixing mill for continuously grinding thoroughly mixing and compacting the ground particles and comminuting or pulverizing the chaff to render the chaff practically invisible in the mixture to packages or containers in a all in a single handling.

Another object of the invention is to provide a combined grinding and mixing mill with coordinated feeding, grinding and mixing mechanisms and with means for cooling the material from the time it enters the mill until discharged in the final mixed state. 7

In grinding coffee beans in retail grocery or coffee stores, the grinding medium usually consists of a pair of cast iron or steel disks of such construction as will best out or granulate the coffee and chaff, and the product consists of a mixture of various sized particles ranging all the way from dust to the largest granulesor flakes that the adjustment of the plates will allow to pass through.

These retail mills are usually provided with a large receptacle under the discharge spout. When the product is discharged from the mill spout into the receptacle, a decided separation large amount of chaff and dust adheres to the inner sides and upper portion of the receptacle while the heavier coffee granules descend into the lower portion of the receptacle.

When a given quantity of coffee has passed through the mill and is then emptied from the receptacle into the usual paper bag, tin can or cardboard container, the materialadhering to the receptacle has to be knocked ofi and usually falls down on top of the heavier product already in the container. This separation between the light and heavy particles is unsightly, causes suspicion in the mind of the retail buyer, and of course the mixture is no longer uniform.

Wholesale coffee manufacturers and toasters coffee and other dry materials;

not uniform when it reaches the ground coffee and chafi through continuous mixers, or batch mixers, as the case may be, to get a thorough mixing and incorporation of the chaff with the cofiee before putting the product up in get a more homogeneous mixture by running packages. Such a mixing machine usually consists of a large drum having an inlet opening at one end and a discharge opening at the other end, and containing a plurality of rotatable spiral flanges. In mixing machines of this type the space or volumecapacity in the mixing chamber is large as compared to the volume of material being mixed. The result is that while the material is being agitated it is constantly tossed in the air without reducing or comminuting the chaff and, when the gate is opened and the material passedfrom the mixer into any kind of friction drops more slowly than the heavier material and a continuous separation results. Con- .sequently,

even when the chaff is thoroughly in-' corporated with the coffee in the mixing drum, a' separation of the light and heavy particles takes place when the goodsare dropped through the air into the receptacle so that the product is the consumer.

The present invention provides an mixer which may be used as a separate unit or in direct association with any suitable grinding mill from the smallest mill used in retail grocery and coffee stores to the larger mills used in wholesale roasting plants, and overcomes all the disadvantages referred to above.

'In the preferred form of the invention the dry material, such as groundcofiee and chaff,

is delivered to a drum or chamber which is small' in diameter in proportion to its length .and is provided with rotatable mixing and conveying devices of any suitable type. The mixing chamher is long enough to thoroughly incorporate the chaff with the coffee, and small enough in diam- .eter so that the material substantially fills the chamber. This tendency to fill the chamber is further increased bya restricted discharge opening which is provided at the end remote from the inlet, and which tends to slightly back up the product and accumulate a mass of material which when agitated by the mixing and conveying devices will reduce or comminute and conceal the chaff. When the mixer is directly associated with .a grinding the air produced by the mill plates tends to further slightly pack the material in the mixing chamber.

improved mill, as hereinafter described,

The mixing, agitating and conveying of the 55 improved keeping qualities.

material is accomplished by means of relatively small flights. In the preferred form of the invention these flights consist of rods which are bentat various angles so as to readily move the material away from the inlet opening, and then to move the material more slowly as it nears the discharge end of the mixer. This action results in slightly compacting the entire product so that as it passes from the discharge spout and drops through the air, it passes down in a solid stream, almost like a stream of water, and there is no separation of the light chaff from the heavier coffee particles.

As an example, the usual prior coifee grinding mill, grinding coffee at the rate of 500 pounds per hour, and discharging into a barrel, displaces a lot of air as the material falls into the barrel. The velocity of the stream of material going into the barrel causes the lighter material to drop slowly into the displaced air coming out of the barrel, increasing the separation, and the sides of the barrel become coated with chair and fine material. Under exactly the same conditions, when the improved mixer of this invention is employed on the outlet of the grinding mill, the material drops in a solid stream to the bottom of the barrel and the displaced air has no tendency to cause the light chaff, etc. to adhere to the sides of the barrel, and the resulting product is a homogeneous, non-stratifying mixture.

In one form of the invention the continuous mixer and compactor is used on a grinding mill having a special shaking mechanism for feeding the coffee or other material from a hopper to the grinding plates. The shaker-feeder, grinding plates and mixing apparatus operate in synchronism, the continuous vibration of the shakerfeeder preventing the coffee or other material from becoming packed and insuring a steady, uniform flow of material from the time it enters the machine until it is extruded as a homogeneous mass wherein the chafi is substantially invisible.

In the preferred form of the invention the combined grinding mill and mixer are water jacketed in a special manner which enables the machine to turn out a much cooler product than has heretofore been possible, and to begin this cooling at the point where the material first begins to be reduced. The lower the temperature at which coffee can be ground and mixed, the smaller will be the amount of carbon dioxide, aroma, etc., escaping from the coffee, these considerations affecting what is usually called the freshness of the coffee. By cooling the material from the time it entersthe mill until it leaves the mixer it is possible to turn out a product having greatly These,and other features and advantages of the invention will be described in connection with the accompanying drawings, in which:

Fig. 1 is a longitudinal section through a grinding mill embodying the invention;

Fig. 2 is a transverse section on the line 2-2 of Fig. 1 showing the water jacket adjacent one of the grinding plates;

Fig. 3 is a longitudinal section through the 'mixer, on a greatly enlarged scale;

Fig. 4 is a transverse section through the mixer taken on the line 4-4 of Fig. 3;

Fig. 5 is a transverse section through the rotatable mixing shaft taken on the line 55 of Fig. 3;

Fig. 6- is a detail section taken on the line 6-6 of Fig. 1;

Fig. 7 is a side view showing a modified mixer head with the discharge spout at the side;

Fig. 8 is a transverse sectional view of the head respectively, showing a mixer head having an adjustable discharge opening adjacent the top;

Figs. 14 and 15 are sectional end and side views, respectively, showing a modified mixer head with a special bearing for supporting the end. of the mixer shaft inside the drum;

Fig. 16 is a plan view of the adjustable shutter plates used in Figs. 9 to 15 inclusive;

Fig. 1'7 is a fragmentary side view of a grinding and mixing mill having a shaker feeder;

Fig. 18 is a transverse section on the line 58-48 of Fig..17; and

Fig. 19 is a fragmentary section on the line |9--|9 of Fig. 17.

For purposes of illustration the invention is shown embodied in a grinding mill of the general ,8. The motor 5 may be enclosed in a housing 9 and is preferably mounted on a platform I! which is hinged at H to the base of the housing and may be; raised or lowered by means of a threaded rod T3 to adjust the tension of the belt l as required.

The shaft 3 is mounted for rotation in a sleeve H which is supported in bearings E5 on the frame of the machine. This sleeve is keyed against rotation by screws l6 having headed portions which rest in longitudinal slots IT in the sleeve and thus permit the sleeve to move to a limited extent in a longitudinal direction without rotating. The sleeve I4 is mounted on bearings on the shaft 3 and has internal shoulders I9 which engage the bearings to move the shaft in a longitudinal direction with the sleeve.

Below the feed hopper 2 is a feed screw 26 which is attached to the shaft 3 and moves the coffee beans or other material toward the grindingplates 2| and 22 contained within the housing 23. The grinding plate 2| is stationary and bolted or otherwise secured to the frame of the machine, while the rotatable grinding plate 22 is removably secured to a hub 24 on the shaft 2. The grinding plate 22 may be bolted to the hub 24 and the hub may be held on the shaft 3 by a set screw or other suitable means. seen from the above that longitudinal movement of the sleeve |4 causes a corresponding movement of the shaft 3 which controls the spacing between the grinding elements 2| and 22 and therefore controls the grade of product, fine or coarse, as desired. The feed of coffee or other material to the feed screw may be regulated by a gate 24' at the mouth of the hopper 2. V

The casing to which the stationary grinding plate 2| is attached is preferably provided with a cooling jacket 25 surrounding the bottom and sides of the feed screw 20. This jacket has an inlet 26 at the bottom and outlets 21 and 26 at the top of the respective branches on opposite sides of the screw conveyor. Cold water or other cooling 'fiuid' is admitted through the Itwiiibe' inlet 26 and the ascending heated fluid is with- 75 index plate obtainable;

aiiaiio drawn through the outlets 2i and 28. A cooling jacket 29 is also provided on the removable head of the housing '23 which surrounds the rotatable grinding plate 22. Water or other cooling fluid is admitted through an inlet ill at the bottom of jacket 2t and the ascending heated fluid is withdrawn through an outlet 32 at the top of the jacket. This jacheting cools the coffee or other material from the time it enters the mill until it is reduced to the desired size by the grinding plates.

The position of sleeve M and shaft and consequently the spacing between grinding elernentsQi and 22, is controlled by a lever 33 which is pivoted 36 to the frame of the machine. The upper end of lever is seated between two depending lugs 35 on the under side of sleeve id, while the lower end of this lever is seated in a bloclr which is threaded on an adjusting rod 3i. The rod 3i extends through the walls of the hollow irame i and has a nut and washer on one end and a thrust block. so and -washer J-l adjacent the other end.

A spring G2 is compressed cetween the block so and washer ll and tends to move the rod 3i toward the left as viewed in Fig. l. The lever 83 transmits this movement to the sleeve i l in an opposite direction, so that the tendency of spring 52 is to move the sleeve M3 and shaft 3 toward the right in Fig. l and thus to move the rotatable grinding plate 22 toward the stationary grinding plate 2 i. This movement is opposed by a second spring 63 which tends to force the sleeve i l toward the left in Fig. l, and, though insufiiclent to overcome the spring 62, serves to cushion the movement of the sleeve [14. These springs also guard against mutilation oi the grinding plates 2i and 22 by bits of iron or other hard foreign materials, allowing the grinding elements to separate until the obstruction has passed through.

The hand wheel l5 which controls the adjustment or" the threaded rod ill is oi the type disclosed in the above-mentioned patent to Burns and Hera. This wheel is secured to the rod ill in any suitable manner and has a plurality of teeth on its periphery. A latch is is pivoted on the frame l and is adapted to fit in between the teeth on the wheel 65 without any lost motion so as to lock the wheel 15 accurately in any adjusted position. A thumb screw All clamps a scale or Gil against the hand wheel 65 to hold this plate in adjusted position. Letters or any other appropriate indicating symbols are placed on the index plate it for the purpose of designating the grade of coarse or fine product obtained when the latch or pointer at is beside a particular letter.

A second latch 59 of U-shaped cross-section is pivoted on the latch alt with the sides or" the U longer than the depth of the latch 56 so that when latch GE goes over a tooth on the hand wheel 15, instead of between the teeth, the second latch 69 will span the first latch and without any lost motion fit on opposite sides of the tooth over which the first latch is held. in this way an increased number of grades of product is as regards the desired size of the coffee granules. In operation, the hand wheel 65 is turned until a desired mark, A, B. C, etc, is opposite the latch (it, rotation of threaded rod El moving the block 35 and causing lever 33 to move about its pivot in a direction to effect the desired adjustment of grinding plate 22 toward or away from grinding plate 20. The latch is proper tooth on the hand the desired then engaged in the wheel, setting the mill to produce grind.

The mixing, compacting and chaii reducing device comprises an elongated drum or tube ill having an inlet pipe 52 arranged to be connected to the mill discharge chute below the mill plates 2i and 22, a rear head a l secured to the frame of the machine, and a detachable front head 55 fitting over the outer end of the drum 5i and clamped to the rear head by means oi rods 56 which are tightened by wing nuts 5i. The front head is termed into a discharge spout ht! which opens downwardly and has an inside and elevated restricted discharge opening 59 communicating with the interior or" the drum 50. in Figs. 3 and i the opening 59 is above the bottom oi the drum 5i and is m the form oi a semi-circle covering the upper half of the rear wall of the front head 55. The drum 53 is surrounded by a jacket ill for the circulation oi water or other cooling fluid which is admitted through an inlet in the bottom and with drawn through an outlet at the top, the inlet being at one end of the drum and the outlet being at the opposite end.

The rotatable mixing shaft is preferably made in two sections it and which are coupled together by a bayonet joint or similar connection so that they may be readily separated and the mixing and compacting device removed as a unit when the clamping rods Eli are detached. The shaft sections lid and are journaled in the front and rear heads 55 and 5%, respectively, and are driven from the main shaft 8 or the grinding mill through a belt till anda pulley it; which is secured to the shaft section G5. it willthus be evident that the shaft t l inside the drum iii is rotated continuously during the operation of the grinding mill.

The mixing, agitating and conveying of the material within the drum at is accomplished by means of relatively small flights which, as shovm in Figs. 3 and 4, preferably consist of rods bent at various angles with their stems projecting through the shaft to and secured thereto by set screws it. The outer ends of these rods are looped in the general form of a sickle so that they both mix and move the material without tossing it about and therefore prevent aeration. These small flights pass through the material and cause the portions engaged by the flights to rotate while the portions between the flights are interrupted in their free rotation by their weight or inertia and thus the particles or chaff are subjected to an abrading action by the rotating coffee granules against the chaff to reduce and congle the chaff with the cofiee particles into a product in which the chafi is substantially concealed without reducing the codes granules' which are preserved in granular form. The angular setting of the flights is such that they move the material away from the inlet pipe 52 at a fairly rapid rate, and then, as the material nears the discharge opening 5%, the tendency of the flights is to move the material more slowly. The result of this action is to compact the material at the discharge end of the drum at so that the material emerges from the opening as and discharge spout he in a solid stream, almost like a stream of water, and there is no separation of the light chad from the heavier cofiee particles. This compressing or compacting efiect is increased by the air produced by the grinding iii.

plates 2i and 22 and is further increased by the restriction oi the opening 59.

In the construction shown in Figs. 3 and 4 the steady stream of mixed material emerging through the opening 59 will be broken by the shaft (it which extends through the center of the spout 58, but this slight splitting or dividing of the stream will not separate the fine and coarse particles which were thoroughly mixed and compasted in the drum at. If desired, however, the front head 55 may be replaced by a head 520i the type shown in Figs. 7 and 8. This head has a restricted opening 473 on only one side of the shaft 6d so that the shaft will not divide the stream of material'which flows from the or m 50 to the discharge spout T141.

Figs. 9 to 16 show various arrangements for adjusting the discharge outlet of themixing and compacting device so that it may be increased or restricted in size .to accommodate it to any desired capacity or output.

Figs. 9 to 11 show a front head 75 which is generally similar to that shown in Figs. 3 and 4;, except that the rear wall of the head is replaced by a narrow annular flange it so as to leave a large opening between the drum i and the discharge spout ill. This opening is arranged to be closed by a pair of overlapping shutter plates l8 and U9 having concentric holes 80 which surround the shaft 65 and arcuate slots 82 which coincide progressively as the plates are rotated about the shaft 66. The plates it and 1'19 are secured to the upper edge or the flange it by means of a wing screw 83 which extends through the slots 82 and may be tightened to hold the plates in any adjusted position.

The plates l8 and 719 are each slightly larger than a semi-circle so that their lower edges will overlie each other and complete the circle when their overlapping upper edges are in the limiting position shown in Fig. 16 with the inner edges of the slots 82 engaging the screw 83. in this limiting position the drum 5!! would be completely shut off from the discharge spout 'll except for the fact that a small gap would exist between the lower portionoithe flange l6 and the plate '89 in the area marked a: in Fig. 9. This gap would occur because the plate. it stands out from the flange it for a distance equal to the thickness of the plate it, and the material in the drum 5i would escape through this gap into the discharge spout W unless prevented. In the preferred form of the invention this gap is closed by a small arcuate shield 86 which is welded or otherwise secured to the lower edge of the plate 39 so that it closes the gap 1: when the plates it and 719 are in the closed position shown in Figs. 9 and 16.

It will be seen from the above that the shutter plates in and it may be adjusted as desired to vary the size of the opening between the drum 5i and the discharge spout ii and thus vary the m compactness and rate of discharge of the prodnot. The proper adjustment can be found merely by looking at the discharged product. It is not wise to compact the product any more than nec-'- essary as it requires more power and tends to heat up the drum 5i. Hence when the opening is restricted sumciently, until there is no separation of the particles of chad and cofi'ee, there is no necessity for any further reduction in the size of the discharge opening. At the proper point, the coiiee is ground by the mill, fed to the rear end of the mixer, moved away from the mill dis charge by the flights, advanced through the mixer at a lower rate of speed as it nears the discharge or front end of the mixer, and then issues from the discharge spout in a fairly solid stream as it passes to the receptacles below.

Figs. 12 and 13 show a construction which is the same as Figs. 9 to 11 except that the shutter plates l8 and 779 are inverted so that the adjustable opening is adjacent the top of the'head it between the drum 5i and discharge spout it. The adjustment is effected in the same manner as described above.

Figs. 14 and 15 show a modified front head 85 having .an integral rear wall it separating the drum 50 from the discharge spout ti and provided with an arcuate opening 88 in its lower portion. This wall has a central bushing 859 which extends into the drum 5i and serves as a bearing for the end of the shaft 641. The adjustable shutter plates lit and 79 are attached to the wall 36 in the same manner as shown in Figs. 9 to 13 and may be adjusted to vary the size of the opening 88 as previously described. It will be evident that the opening 88 may be at the top of the wall 86 instead of at the bottom; in which case the adjustable plates it and i9 will be inverted in the manner shown in Figs. 12 and 13. Since the shaft t6 does not extend into the discharge spout 8i it cannot break the stream of material issuing from the opening 88.

The mill shown in figs. 17 to 19 is similar to that shown in Fig. l but is provided with a special shaking mechanism for feeding the coffee or other material from the hopper to the feed screw and grinding plates contained within the housing 23 of the mill. The hopper at is supported by rods 92 which are adjustably mounted in brackets d3 on the frame of the machine. Beneath the hopper is the shaker-feeder a l having a spout 95 leading into the housing 23 directly above the feed screw which conveys the fed-in material to the grinding plates.

The shaker-feeder 943 is connected to the hopper ill by a strip of leather or other flexible material 98 and is supported on the bottom by a vibratable bar 9'17 of steel or other suitable material A lug 9% is welded or otherwise secured to an intermediate portion of the bar 97, and this lug is pivoted by a pin tit) to a bracket Mil which is adjustably mounted on the supporting rod 92 on one side of the machine. By adjusting the bracket iiil and bar W up or down the shaker-feeder 96 may be raised or lowered slightly as desired.

A bolt Hi2, secured to'the bottom of the shaker- .feeder 96, passes through the upper end of the bar 971 and this bolt is surrounded by a compression spring Hi3 which forces the bar 9? against the shaker-feeder while permitting it to vibrate freely. The lower end of the bar 97 contacts with a cam Hi6 which is mounted on the mixer shaft section 65 and has fiat faces which cause the bar ill] to vibrate continuously. The continuous vibration of the shaker-feeder prevents the coilfeeor other material from becoming packed and insures a steady, uniform fiow of material through the spout 95 in synchronism with the grinding and feeding operations.

The flow of material from the hopper 9: may be restricted or entirely shut oif by a door ltd which is operated by a handle ltd and is adjusted in any desired position by means of a wing nut MW and cooperating bolt which is secured to the side of the hopper and passes through a slotin the door.

It will be evident that the invention is capable oi various other modifications and adaptations 45 mg the cofiee and liberating the chaff, a discharge allelic v not specifically described but included within the mixing drum of. substantially g eate length than scope of the appended claims. width having an inlet opening at one end for The inve tio l i d connection to said discharge chute, a rear head l. The combination with a coffee grinding mill on said frame for closing the inlet end of the having relatively movable grinding means for drum, a detachable front head for the discharge 5 granulating the coffee and liberating the chaff d f the drum av ng a e c ed discharge and a discharge chute below said grinding means. p n t lly smaller than the cross-secof a mixing drum of substantially greater length n l a of the drum, rods f r clampin i than width having a i let Opening t one nd drum between said front and rear heads, a roconnected to said discharge chute and a restricted t b shaft 011 Sa d fr e av a Section 3 m discharge opening at the other end, and conveynaled in said rear head and a separable section ing and agitating devices in said drum for acting g lengthwise throug t (1mm and 3 m- E t redu e the naled in said front head, a plurality of conveying on the mixture of coffee and cha chair and min the coffee and chaff andmoving it n agitating fli ht n i p r le shaft secthe drum at various angles from the inlet end toward the discharge end, said tion projectin n o conveying and agitating devices being arranged fol acting on the mixture of coffee and chaff to to move the material more rapidly toward the reduce the chad and mix the coffee and chat discharge end at the inlet end or" the drum than and moving it from the inlet end toward the disat the discharge end so as to compact the mah rge end, the ni h s dj c n he inl nd of 2% terial at the discharge end. the drum being arranged to move the material 2b 2. The-combination with a cofiee grinding mill more rapidly toward the discharge end than the having relatively movable grinding means for flights adjacent the discharge end to compact the granulating the coffee and liberating the chaff material at the discharge end, and means for adand a discharge chute below said grinding means, lusting the setting of said flights to vary the comoi a mining drum of substantially greater length pactness of the mixed material. 5

than width having an inlet opening at one end 5. A method of treating roasted coffee beans,

adapted for connection to said discharge chute including the following steps: first granulating and a restricted discharge opening at the other the cofiee beans, and second working substantially end substantially smaller than thecross-sectional all of the granulated cofiee and any liberated area. of the drum, means for detachably conchafi together for a period of time sudicient to 39 netting the drum to said mill and ior coupling pulverize the chart and commingle it with the said inlet opening to said discharge chute, and coffee. conveying and agitating devices in said drum for 6. The method of preparing a mixture of gran acting on the mixture of coilee and chafi to reulated cofiee and chafi which comprises reducing 35 duce the chafi and mix the coffee and chaff and the cofiee beans and liberating the chaff, accumumoving it from the inlet end toward the discharge lating in a mass substantially all oi said granu- Said Conveying an agitating devices being lated cofice and chaff, and subjecting said mass arranged to move the material more rapidly toto agitation for a m m -1 g of t t g. Ward the discharge end at the inlet end of the verize the chafi and mix the same with the cofiee.

i0 drum than at the discharge end so as to compact In a device for granmatmg cofiee beans and 2 if i zg g a fig m mixing granulated coffee and chafi, means for recwee ng an T m compns' ducing col-lee beans and liberating the chat? ing a lrame contalning ahousingrelatlvely movtherein an riot t wsin m1 t t able grinding means in said housing for grarnilatpe e 8 means a one end of said casing connecting with said re A5 chute on said housing below said grinding means, ducmg means for ecewmg the mixture f a, mixing drum of substantially greater length ulated cofiee and liberated chafi, restricted dismm Width having an inlet gpening adjacent one charge means at the other end of said casing, a

end for connection to said discharge chute, a rear rotatable Shaft Within Said casing, conveying and so head on said frame for closing the inlet end of ag t e ements Carried by Said shaft for act 5@ said drum, a detachable front head for the other ing on the mixture of cofiee and chafi to reduce end of said drum having a restricted discharge the chaff and mix the coffee and chaff. opening substantially smaller than the cross-sec- 8. A cofiee grinding mill of the character detional area of the drum, means for clamping said scribed, comprising in co bination, a grinding drum between said front and rear heads, a rotatmeans provided with a feeding inlet for material 55 able shaft on said frame having a section jourt b ground ds, di char therefro a, connaledln said rear head and a separable section veyor h b having an intake adjacent one end extending lengthw se gh t e u and l and a discharge adjacent the other end thereof, naled in said front head, and a plurality of 0011- t discharge from t i i ans opening to vevine and a ta devices on said separable directly into the intake of said chamber, and a co.-

shait section for acting on the mixture of cofiee feeding means within t chamber including and shall to reduce the chafi and mix-the coffee quick feed means adjacent th i t ke d, of th and chaff d moving it from h inlet end chamber and slow feed means adjacent the disthe dr m wa d the d c a e Said 0011- charge of the chamber, said means comprising 35 veying and agitating devices being arranged to members rigidly mounted on common dri 5 m v th mat r a m r p dl a d t shaft and including elements extending radially charge end at the inlet end of the drum than at t a i t adjacent the inner surface oi the th d s har nd so a to mp t e m a chamber and. having surfaces extending longituat thedischarge end. dinally of the chamber and inclined with respect 7o 4. The combination with a coffee grinding mill to the axis thereof, the inclination or pitch of np s ne a m a h usin on said fram the elements being such that these adjacent the relatively movable grinding means in said housintake end feed the material at a more rapid rate s f r e ul ing the c ff e and lilwratine the than those adjacent the discharge end, both of chafi, and an enclosed chute on said housing to said feed means feeding toward the discharge end discharge the mixture of cofiee and chaff, of a of the chamber and arranged to cooperate with 75 6 2,114,110 each other and the chamber wall to accumulate and chair and produce a homogeneous pwdlw and compact the ground bean and chaif. wherein the chafl is substantially invisible while 9. The method of preparing a mixture of granpreserving the granular form of the coffee. ulated cofiee and chaff which comprises granu- 11. The process of preparing coflee that has lating the cofiee to liberate the chafi and to probeen broken up into coflee particles of relatively duce coffee granules 'of desired size, and then uniform size as well as into particles of chafi while preserving the granular form of the coffee. mass about said axis and subjecting it to agita- 10. The method of preparing a mixture of grantion to cause relative movement between the cofulated coffee and chafi" which comprises granufee particles and liberated chaff for a period of lating the coffee to liberate the chafi and to protime sufiflcient to subject the particles of chafi to duce coffee granules of desired size, accumulatsuch an abrading action by the rotating cofiee ing a mass of the coffee granules and chaff, and particles as to reduce and commingle the chafi then working the coiiee granules in the mass with the cofiee particles into a product in which against the commingled chafi for a period of time "the chafi is substantially concealed. sufficient to reduce the chaff and mix the cofiee ARCHIBALD D. i. A H A 

